Furnace closure



Jan. 26, 1960 F. ENDTER 2,922,386

FURNACE CLOSURE Filed Nov. 15, 1956 2 Sheets-Sheet 1 I N VENTORFK/EDF/Ch' E/VD 757?,

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ATTORNEY Jan. 26, 1960 F. ENDTER 2,922,336

FURNACE CLOSURE Filed Nov. 15, 1956 Y 2 Sheets-Sheet 2 INVENTOR v 17FF/EO/F/CH EVDZEX;

ATTORNEYS United States Patent FURNACE CLOSURE Friedrich Endter,Konstanz, Germany, assignor to Deutsche Goldand Silber-Scheideanstaltvormals Roessler, Frankfurt am Main, Germany Application November 15,1956, Serial No. 622,423

Claims priority, application Germany November 19, 1955 7 Claims. (Cl.110-98) The present invention relates to improvements in closure meansfor furnaces and more particularly furnaces which are provided withvertically suspended tubes, the free ends of which project through theclosure end of the furnace.

In chemical reactions which are carried out on catalytically activesurfaces at relatively high temperatures, it is often necessary toemploy furnaces in which the reaction space is subdivided into a numberof separate tubes. In such instances where the reaction is carried outat temperatures at which metal tubes cannot be used, whether it be forthermal or chemical reasons, such furnaces are equipped with ceramictubes, for example, tubes of sintered alumina, sillimanite and the like,which, if necessary, are associated to form bundles of tubes. Specialprecautions are necessary in the use of such ceramic tubes in reactionunits in view of their comparatively high sensitivity to mechanicalshock and impact and in view of their low resistance to temperatureshock. Therefore it has been usual to support the tubes only at theupper end of the furnace and to permit the lower free ends to extendfreely from the bottom of the furnace so as to prevent high stresses oreven destruction of the tubes upon occurrence of temperature strains.

As a consequence, certain requirements must be met in the closureprovided at the end of the furnace from which the free end of the tubesextend, as such closure must on one hand be such as to seal off thefurnace heating chamber as tightly as possible tov prevent untenableheat losses and, on the other hand, must not hinder the mobility of thetubes to such an extent that changes in volume and changes intemperature cannot be compensated for. It has been found thattemperature changes not only cause a movement in the direction of thelongitudinal axis of such tubes but also transverse to such axis. Whenthe lower furnace closure in any way prevents such lateral movement ofthe free lower tube end it can easily result in stresses on the tubes ortheir destruction.

The closures normally employed have not satisfactorily fulfilled therequirement of providing a good heat seal with simultaneous provisionfor the required lateral freedom of movement of the tubes. For example,if the lower end of the furnace is closed with a refractory platerigidly connected to the furnace and provided with openings permittingpassage of the free ends of the tubes therethrough, it was found thatthe lateral play provided for the tubes is still too small even thoughthe closure plate is subdivided a number of times to provide betterthermal stability. If, on the other hand, the openings in the closureplate are selected to be large enough to provide suflicient spacebetween the inner wall of the openings and the outer surface of thetubes, considerable radiation losses occur through the space thus leftfree and such radiation losses are extremely disadvantageous for thethermal efficiency of the furnace.

According to the invention it was found that these difiiculties can beovercome in a simple manner by pro ice j sutficiently large to providethe desired lateral play for' the tubes. The insulating bodies whichrest loosely upon the supporting element are larger than the openingspro,- vided in the supporting element and of thesarne crosssectionalshape. Each insulating body is provided with an opening permittingpassage of a single tube, the opening however does not have to besubstantially larger than the: external diameter of the tube. It is ofparticular importance accordingto the invention thatthe insulatingbodies are so dimensioned that a space is left between them on all sidesso that they do not touch one another. The

dimension of the space between the insulating bodies;

should be sufficiently large so as not to prevent deflection of anyinsulating body when a tube associated therewith may become distortedand thereby cause the body to move laterally. It has been found inpractical use of the closure means according to the invention thathorizontal spacings of about 2-8 mm. between the lateral surfaces of theindividual insulating bodies are satis-l factory. The multipart closuremeans according to the invention have proved very satisfactory for'thepurposes indicated as they provide a good thermalseal even at highfurnace temperatures and, on the other hand, they are also, able toyield to every movement of the tubes caused by volume changes of suchtubes so as to avoid danger of destruction of the tubes.

Furthermore, the closure means according to the in vention can beemployed to close furnace chambers of any desired size without producingthe mechanical or" thermal sensitivity as exists with unitary shapedclosure elements such as insulating plates and the like conforming insize and shape to the furnace chamber to be closed off.

As already indicated, it is essential that the shaped bodies which forman important element of the closure means according to the invention areof the same crosssectional form as in this way, depending upon thearrangement of the tubes in the furnace, it is best possible to providean adequate seal against heat losses. Shaped bodies whose horizontalcross-section is in the form of V a regular hexagon have been foundparticularly suitable for the purposes of the invention, as despite thegap which must be provided between the vertical boundary surfaces ofsuch hexagonally shaped bodies, they can be as'so-,

ciated together to form an optimal tight packing. The"v supportingelement is preferably also adapted to this form of the shaped bodies inthat it is in the shape of a lattice I grid in which the grid bars areconnected to each other in honeycomb fashion.

element preferably have trapezoidal cross section, the

tapered side of which is on the side facing away from the furnace.

In order that the heat loss which might still occur through the spacesprovided between the shaped in sulating bodies be kept as low aspossible, it has proved expedient to provide projections andcorresponding recesses in the adjacent vertical surfaces of the shapedbodies to provide -a telescoping tongue and groove 'joint therebetween.It is also possible to offset the boundary surfaces of the adjacentshaped bodies so that the slots or spaces between the bricks appeardiscontinuous or staggered laterally in relation to one another.Furthermore, it is also possible to provide complementary re.

The grid bars of the supporting.

cusses at anysuitable 'height in the sides of the adjacent spacedinsulating bodies in which horizontal closure plates can be looselyplaced in such a way as still to permit the desired relative movementbetween the individual shaped insulating bodies.

Furthermore, it has been found expedient to shape the bores in theinsulating bodies intended for passage of the furnace tubes conically sothat they flare outwardly on the side of the shaped bodies facing theinterior of the furnace. This construction has been found particularlyfavorable for the provision of a temperature distribution at the furnaceoutlet which takes the sensitivity of the ceramic tubes to temperaturevariations into account.

It is obvious of course that the size of the openings in the supportingelement facing the insulating bodies is smaller than the horizontalcross-section of the insulating bodies associated therewith andconversely that the size of the opening at the botom of the insulatingbody must be smaller than the opening in the supporting element withwhich it is associated.

The accompanying drawings serve to illustrate the closure meansaccording to the invention.

In such drawings:

Fig. 1 is a top View of a closure means according to the invention withsome of the individual insulating bodies removed for sake of simplicity;

Fig. 2 is a vertical cross-section through a portion of the closuremeans according to the invention illustrating the relationship of afurnace tube therewith;

,Fig. 3 is a vertical cross-sectional view through a portion, of aclosure means according to the invention illustrating the modificationof the individual insulating bodies which are provided withcomplementary recesses and projections; and

Fig. 4 is a sectional view of a furnace with the closure means accordingto the invention mounted therein.

,In Fig. 1, 11 designates the grid bars of the supporting element 18which are connected to one another to form a honeycomb shaped latticedefining hexagonal openings 12 to permit passage of the furnace tubes.The openings 12 are as large as possible and the bars 11 are as narrowas possible in order to provide for small contact surfaces for transferof heat between the insulating shaped bodies 13 and the supportingelement. The insulating shaped bodies which are of hexagonalcrosssection rest on grid bars 11 in such a way to leave gaps 14 betweenthe vertical surfaces of the adjacent insulating bodies to permitlateral movement of such shaped bodies relative to each other. Eachinsulating body is also provided with an opening 15 to permit passage ofa furnace tube therethrough and through the opening 12 in the supportingmember associated therewith.

Fig. 2 which shows a vertical sectional view of a portion of the closuremeans according to the invention shown in Fig. 1, shows the trapezoidalform of grid bars 11 as well as the outwardly flaring top portion ofopening. 15 in insulating bodies 13 which rest upon the sup-. portingmember covering openings 12 therein. This figure also shows a furnacetube 10 associated with the closure means passing through openings 12and 15. Asindicated in broken lines, insulating bodies 13 can beprovided on their facing surfaces with pocket-like recesses 16, intowhich a loose fitting sealing plate 17 is inserted so as not to hinderlateral movement of the insulating bodies while at the same timebridging gap 14.

In Fig. 3 the insulating bodies 13' have been provided withcomplementary projections 17' and recesses 16' to provide a telescopingtongue and groove joint therebetween.

Fig. 4" shows how the supporting element 18 is loosely aszaese carriedon an angle member 19 which is rigidly connected with furnace body 20.Such figure furthermore illustrates how the furnace tubes 10 aresupported in the furnace by a common head 21.

I claim: s

1. In combination with a furnace of the type described having verticallysuspended tubes projecting freely from the furnace at its lower end, aclosure means for such lower furnace end comprising a horizontalsupporting element having spaced openings resting on holding means fixedto the furnace, -each of said openings permitting passage of one of thefurnace tubes therethrough and each of said openings in the supportmember being large relative to the diameter of the furnace tube passingtherethrough to allow for substantial lateral displacement of the tube,and a plurality of insulating bodies of the same horizontalcross-sectional form as said openings but larger than said openingsloosely resting upon the horizontal surface of the supporting element,each provided with an opening smaller than the openings in saidsupporting element permitting passage of one of the furnace tubestherethrough, each resting over an opening in the supporting element incontact with the periphery is in the form of a lattice work grid withgrid bars conof such opening and having its opening in alignment withsuch opening in the supporting element, the lateral surfaces of suchinsulating bodies being spaced in the horizontal direction from thelateral surfaces of the insulating bodies adjacent thereto to permitindividual lateral relative movement of each individual body uponlateral movement of the furnace tube passing through the openingtherein.

2. A device as claimed in claim 1 in which the spacing between thelateral surfaces of the adjacent insulating bodies is 2 to 8 mm.

.3. A device as claimed in claim 1 in which the horizontalcross-sectional form of said insulating bodies conforms to a regularhexagon and the supporting element nected in honeycomb fashion.

4-. A device as claimed in claim 3 in which said grid bars are taperedtoward the bottom.-

5. A device as claimed in claim 1 in which the lateral surfaces ofadjacent insulating bodies are provided with complementary recesses andprojections which overlap each other but are so dimensioned as to permitthe individual lateral relative movement of the insulating bodies.

-6. A device as claimed in claim 1 in which the lateral surfaces ofadjacent insulating bodies are provided with aligned horizontal slotlike recesses and the adjacent insulatin'g bodies are bridged by a platemember telescoping into'the aligned recesses in the adjacent lateralsurfaces of such insulating bodies, said recesses and plate membersbeing so dimensioned as to permit the individual lateral relativemovement of the insulating bodies.

7. A device as claimed in claim 1 in whichthe opening in the insulatingbodies flares outwardly in the direction away from the supportingelement.

References Cited in the file of this patent UNITED STATES PATENTS

